The primary goal of the proposed research is to further our understanding of the nature and basis of the development of intersensory perception and attention and its consequences for learning and memory about audible and visible events. Prior research has primarily focused on identifying intersensory capabilities of infants without directly examining the learning process or developmental change and without integrating insights from psychobiological or neural research. The present proposal will assess the origins, nature, and development of intersensory perception in young infants and will evaluate predictions generated from our "intersensory redundancy" hypothesis which integrates findings from the comparative and neural research with those on human development. It is proposed that in early development, intersensory redundancy selectively recruits infant attention to amodal properties and facilitates further processing, learning, and memory for those properties. In contrast, unimodal stimulation facilitates attention, learning, and memory for modality-specific properties. Since most events are multimodal, this gives a processing advantage to amodal over modality-specific properties in early development. This has important consequences for learning and memory and for more complex processes such as language and social development, since the perceptual bases of these abilities emerge from a multimodal context in early infancy. In the proposed research eight experiments will evaluate these hypotheses using an infant-controlled habituation procedure. The research will assess the emergence and developmental change in infants' sensitivity to amodal and modality-specific properties in the context of multimodal as well as unimodal stimulation. The effects of intersensory redundancy on attention, perception, learning, and long-term memory will be assessed for social and nonsocial events. Together, these findings, regardless of whether they support out hypotheses, will shed light on the origins and function of the salience of intersensory redundancy. Results will be considered in light of those from Lickliter's psychobiological findings, Rochat's behavioral findings, and Mundy's social/clinical findings, with the goal of establishing general principles of development and providing a basis for evaluating atypical or delayed patterns of early perceptual organization.